This application is a 35 U.S.C. 371 application of PCT/DE 00/02677, filed on Aug. 10, 2000.
1. Field of the Invention
The invention is based on hydraulic control devices for controlling injection of fuel into internal combustion engines.
2. Description of the Prior Art
DE 38 44 133 A1 has disclosed a metering injection valve for an internal combustion engine that is equipped with a hydraulic control device of the type with which this invention is concerned. This control device has an actuation device, which acts on the valve body of a valve part in order to control the parameters of the injection process, for example the injection onset or the injection-duration.
In order to permit a clean-burning and fuel-saving operation of an internal combustion engine, it can be advantageous to divide the injection process into a number of injection phases that follow one another in chronological sequence. The rapid switching events required for this can be achieved, in particular, by using piezoelectric actuators as actuation devices. However, it is disadvantageous that these piezoelectric actuators produce a relatively large amount of heat loss, which increases as the frequency of the triggering pulses rises. Under extreme operating conditions, this can lead to thermally-induced failures of the actuation devices.
The hydraulic control device that forms the basis of the invention has the advantage over the prior art that a single triggering of the actuation device can achieve an injection process that is divided into several injection phases. The frequency of the triggering of the actuation device and therefore the generated waste heat of the actuator is thus reduced and the operational reliability is therefore increased.